I don't know where that figures come from. Linked to a £6m move to Arsenal last season. He just needs a season of regular football and he'll be ready for us.
Most likely option for you is a loan unless you want to spend that sort of money. But I can't see him wanting to leave permanently...
I don't think you'll be able to sign him on a permanent. Maybe a loan deal. This kid is going places. Quality striker. You wouldn't be able to buy him for less than £6m+ with his potential, and how highly all at the club value him....